I have used the ALG QMS, Geissele SSA, SSA-E, LaRue MBT-2S, and a Triggertech Competitive Special (3.5 lb) flat-faced trigger.
I have an ALG QMS in my AR pistol, and it's a good single stage trigger. I've used the ACT in my brother's gun and that's probably the sweet spot if you like single-stage triggers if you swap in a lighter spring (he has a JP Yellow, I believe).
The MBT-2S is my go-to for just about everything these days. I love the fat face, smooth first-stage, consistent break, and VERY positive reset, At under $100, it's the best value 2-Stage trigger out there (avoid the single stage from what I've heard). It's hard to justify the ALG single stage triggers when these LaRue 2 stage triggers are so good for not much more $$$.
The SSA was great, but I sold it to buy 2 more LaRue MBT-2S triggers. The SSA was a little lighter and I'd give it a slight edge over the MBT-2S for overall feel, but when you factor in the price tag, the MBT-2S is about 90% as good for ~40% of the cost.
The SSA-E is definitely a step above the MBT-2S and SSA, and is a fantastic trigger if you can find it on sale. If you only have one gun, the SSA-E or SD-E (SSA-E with a flat face) are great options. If you have a bunch of rifles that need good triggers, the price adds up quickly...
After trying the Triggertech Competitive 3.5 lb trigger, I'm blown away at how crisp the break is & how fast the reset it is. It has a very short first stage compared to the others, which took some time for me to adjust to, but I find myself really impressed by this thing. I think 3.5 lbs is the sweet spot for my uses, but I definitely have their Diamond adjustable trigger on my wishlist for my 6.5 Creedmoor bench-rest rifle. I've heard it's darn near perfect.